Grease gun coupler



FIG. 1 is a front, right and top perspective view of a grease gun coupler, showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines shown in the drawings illustrate portions of the grease gun coupler that form no part of the claimed design. 

CLAIM The ornamental design for a grease gun coupler, as shown and described. 